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MF2222 Biological Control of Insect Pests on Field Crops in Kansas

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MF2222 Biological Control of Insect Pests on Field Crops in Kansas Phillip E. Sloderbeck, James R. Nechols and Gerald L. Greene BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS 3 Table of Contents Conservation of Natural Enemies ...................................................................................... 5 Importation of Natural Enemies ........................................................................................ 6 Augmentation of Natural Enemies ..................................................................................... 6 Important questions to ask when considering an augmentation program ................................................................... 7 Recognition of Common Biological Control Agents ......................................................... 8 Predators .................................................................................................................... 8 Lady beetles ...................................................................................................... 8 Hover flies ......................................................................................................... 9 Lacewings ....................................................................................................... 10 True bugs ........................................................................................................ 10 Ground beetles ................................................................................................ 11 Spiders ............................................................................................................ 11 Parasitoids ................................................................................................................ 11 Parasitic wasps................................................................................................ 11 Tachinid flies .................................................................................................. 11 Pathogens ................................................................................................................. 12 Nematodes ...................................................................................................... 12 Microbial Pathogens ...................................................................................... 12 Examples of Biological Control of Major Pests of Kansas Field Crops .................................................................................. 13 Alfalfa weevil ........................................................................................................... 13 European corn borer ............................................................................................... 13 Green bug ................................................................................................................. 14 Spider mites ............................................................................................................. 15 Russian wheat aphid ............................................................................................... 15 Chinch bug ............................................................................................................... 15 Corn rootworms....................................................................................................... 17 Conclusions......................................................................................................................... 17 Acknowledgements ............................................................................................................ 18 Additional Information on Biological Control ................................................................ 18 BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS 5 Biological Control of Insect Pests on Field Crops in Kansas Phillip E. Sloderbeck, James R. Nechols and Gerald L. Greene Biological Control In the simplest terms, biological control is the reduction in pest populations from the actions of other living organisms, often called natural enemies or beneficial species. Virtually all insect and mite pests have some natural enemies. Learning to recognize and manage these natural enemies can help reduce pests populations and, thus, reduce crop losses and the need for costly chemical and/or other control measures. Biological control is most effective when used with other compatible pest control practices in an integrated pest management (IPM) program. Practices that are often compatible with biological control include cultural control; planting pest resistant varieties and using selective insecticides when other practices fail to keep pest numbers below the economic threshold. To be used effectively, biological control requires a good understanding of the biology of the pest and its natural enemies, as well as the ability to identify the pest’s life stages in the field. Frequent field scouting also is necessary to monitor natural enemies and evaluate their impact on pest populations. Biological control programs are categorized in three basic ways: conservation, importation and augmentation. be accomplished by using selective insecticides such as Conservation of Natural Bacillus thuringiensis (B.t.), timing the application to Enemies avoid periods when important natural enemies would be Conservation of natural enemies is arguably the exposed, or placing the insecticide in a location where most important concept in the practice of biological natural enemies will not contact it. In other cases, control and, fortunately, is also one of the easiest to adequately protecting natural enemies may require not understand. Simply put, conservation of natural enemies using an insecticide. means avoiding practices that harm natural enemies and Certain cultural practices also can be detrimental to implementing practices that benefit them. It may sound natural enemies. Plowing, cultivation, mowing or like good common sense, but the tricky part comes in harvesting operations can be disruptive to natural understanding exactly what practices are harmful and enemies at critical points in their life cycle—if how beneficial practices can be integrated into a detrimental, the practice should be avoided. Excessive production system. This requires understanding the amounts of dust from roads or cultural operations also biology of natural enemies and being willing to modify can reduce control by disrupting the activities of practices to accommodate them. predators and parasitoids. Burning crop residues or The most obvious harmful practice is the use of inappropriately timed irrigation also can kill many insecticides at times when natural enemies will be natural enemies. Finally, the ambiguous category of harmed. Insecticides can have direct effects on natural “clean farming,” which includes removing weeds and enemies by killing them, or indirect effects by non-crop habitats, has been found to be detrimental to eliminating their hosts and causing starvation. In some many natural enemies. Increased crop residues have cases, insecticides can be successfully integrated into been shown to favor ground beetles, spiders and other the system without harming natural enemies. This may general predators. 6 BIOLOGICAL CONTROL OF INSECT PESTS ON FIELD CROPS IN KANSAS To better conserve natural enemies, the following Augmentation of Natural questions need to be answered: Where do the natural enemies overwinter? Do they need alternative prey/food Enemies sources to meet their nutritional needs at times when the To many people, biological control means buying pests are not abundant? Do they need shelter during the and releasing beneficial natural enemies to control insect growing season in the form of wooded areas, surface and mite pests. This approach is known as residue, or weedy field borders? Until these questions augmentation. The underlying reason for the wide are answered, the benefits of the natural enemies of any recognition of this technique is that it relies on pest cannot be realized. commercial products which may be advertised in magazines and publicized in the media. Further, the use Importation of Natural Enemies of pesticides has trained us to think about pest Many insects become serious pests when they are management in the context of purchased products. introduced into a new area which lacks their native However, of the three general approaches to insect natural enemies. Examples of European or Eurasian biological control, augmentation is the least sustainable insects that have become important pests on Kansas because it requires the regular or periodic purchase of field crops include the European corn borer, alfalfa products. Nonetheless, in some pest situations it is a weevil, greenbug, Hessian fly and Russian wheat aphid. highly efficacious, cost effective and environmentally The importation of new natural enemies to control sound approach to pest management. imported pests often is referred to as “classical” The practice of augmentation is based on the idea biological control. Some dramatic successes in that, in some situations, there are not adequate numbers biological control have resulted from importing effective or species of natural enemies to provide optimal natural enemies that are well-adapted to the pest from an biological control, but that the numbers can be increased area where the pest is thought to have originated. (and control improved) by releases. This may require a The goal of classical biological control is to find readily available source of large numbers of natural useful natural enemies, introduce
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